Peel vegetables. Cut parsnips into 1-inch slices; cut turnips, rutabaga, and squash into 1-inch cubes.
Bring parsnip, turnip, rutabaga, 2 quarts water, and 1 tablespoon salt to a boil in a Dutch oven; boil, stirring occasionally, 5 minutes. Add squash, and cook 7 to 10 minutes or until slightly tender. Drain and cool. Chill up to 8 hours, if desired.
Combine remaining 1 tablespoon salt, flour, and pepper in a heavy-duty zip-top plastic bag; add one-third of vegetables to bag. Seal and shake to coat; place in a single layer in a greased roasting pan. Repeat procedure with remaining vegetables and flour mixture. Drizzle vegetables with butter, tossing gently.